Panels of the class to which those of this invention belong, are frequently made of aluminium for light weight, and they are distinguishable from the corrugated sheets used in the more substantial sense indicated above, in that the width of the present panels is small relative to the length, and the pitch and general dimensions of the corrugations are very large; to a degree, for example, such that across its full width a sheet will usually have no more than two complete corrugations.
Panels of the kind in question have longitudinal edge formations whereby each panel in an array thereof is joined to its neighbouring panel or immediately adjacent, and hitherto the panels have proved quite satisfactory except when called upon to withstand loadings beyond those involved purely in the roofage function; for example, when a person imposes his weight on the roof.
Under such abnormal loadings, the prior panels deflect and tend to come apart at the joints. It will also be appreciated that in all roofing arrangements composed of corrugated sheets or panels, edge joining is accompanied by some degree of overlap of sheet edge margins. In the more commonly employed sheets, this overlap is achieved, without substantial impairment of even, uniform corrugation appearance, by overlapping the sheets by at least one whole corrugation; whereas, with panels such as those subject hereof, whole corrugation overlap is economically out of the question since, owing to the large size and the fewness of the corrugations, it would amount to making a twin layer roof, or at least one in which a majority of the roofed area would be of double-layer sheet material.
The object of this invention is to improve the situation indicated by the provision of roof panels in which overlap is confined to an extremely small amount of the roofed area, without substantial impairment of the roof underside appearance of corrugation eveness or continuity; and this, in a lightweight manner while being virtually proof against lap-joint separation under abnormal loadings.